Re: [PATCH, MIPS] Support shared library debug with MIPS PIE

["Maciej W. Rozycki" <macro at linux-mips dot org>]

On Tue, 23 Jun 2015, Matthew Fortune wrote:

> New dynamic tag:
> 
> DT_MIPS_RLD_MAP2 - 0x70000035
> 
> Definition:
> 
> This member is used by debugging.  It contains a relative offset from the tag's
> runtime location of a 32-bit word in the .data section which is supplied by the
> compilation environment. The word's contents are not specified and programs
> using this value are not ABI - compliant.
> 
> I have considered the suggestion from Roland and Maciej about making this a GNU
> tag. MIPS needs this feature because of the way the psABI is defined and will
> therefore need this for any OS which may well then lead to needing more tags.
> If the tag were in the completely generic range (like DT_DEBUG) then I wouldn't
> be concerned at all.

 We've been using GNU extensions (e.g. GNU ELF attributes) for other 
purposes with no concern whatsoever about other OSes.  And they are free 
to adopt them.  So what is your specific concern about DT_GNU_RLD_MAP?

 With that in mind and given that this is a generic feature to support PIE 
while keeping the dynamic segment r/o, do you maintain it would better go 
with the ELF gABI rather than as a GNU extension?  I suspect with a good 
justification, that I believe we have here, reserving a dynamic tag number 
with the gABI maintainers shouldn't take a lot of time or effort.

  Maciej